1. Technical Field
The present invention relates to an air-bag device for, at the time of vehicle collision, immediately pressing the legs of an occupant to absorb collision energy or protecting a side of an occupant, and to an occupant's lower limb protecting device for a vehicle and a device for protecting an occupant at the time of vehicle side collision wherein the air-bag device is used.
2. Background Art
Air-bag devices for vehicles generally comprise an air-bag embedded in a predetermined place in a vehicle interior (for example, a steering wheel, a panel on a passenger's seat side, or the like), an inflator for supplying high pressure gas to the air-bag, an acceleration sensor for detecting vehicle collision, and the like. At the time of vehicle collision, the inflator is ignited by an ignition signal from the acceleration sensor to generate high pressure gas, and the air-bag is thereby instantaneously expanded to prevent an occupant from dashing against the steering wheel, the panel or the like.
As such air-bags, a knee air-bag has been put to practical use which is capable of immediately holding the legs of an occupant on a front-seat (driver's seat/passenger's seat) to absorb energy.
As a knee air-bag of such a knee air-bag device, there has been a fabric knee air-bag, a plastic knee air-bag prepared by blow molding or injection molding or the like.
With respect to a fabric air-bag, since a fabric exerts tension, it is difficult to appropriately determine impact absorbing capacity for receiving knees. Accordingly, in order to optimize impact energy absorption, high development costs are required.
Further, each of these knee air-bags has such a problem that if the knee air-bag does not appropriately expand, it will dash against lower portions of legs of an occupant in the course of expansion or it will advance between knees of the occupant to cause legs of the occupant to straddle or, in a case where the occupant is of small build, it will expand in such a manner that it covers laps of the occupant to bias the laps of the occupant toward the floor of a vehicle.
As a result, the knee air-bags intended to protect the legs of an occupant adversely apply by themselves too heavy a bending load on bones below the knees, or come between the knees, push the legs apart and thereby fail to constrain the portions below knees for sufficient protection.
On the other hand, when the knees are pushed up by the impact force from the backward-going toe board, the expanded knee air-bags restrain the knees from being pushed up, thereby possibly bringing harmful consequences on the occupant such as tibia fracture, fibula fracture, ligamentous injury and the like.
With respect to a plastic knee air-bag, Patent Document 1 discloses such an automotive glove box assembly that an expansible body is connected to a gas emitting unit, and upon discharge of gas, the expansible body is pressurized and its face portion is projected to an extended position so as to constrain the lower extremities of an occupant.
Each of Patent Documents 2 and 3 discloses an inflatable knee bolster for a vehicle occupant which is mounted facing the knees of a vehicle occupant. The inflatable knee bolster is such that at least partially collapsible pleated profile elements are disposed along the sides and across the top of an expansible air-bag inner, and actuation of an inflator pressurizes the air-bag inner to cause at least a portion of the pleated profile elements to collapsibly deform in such a manner that a chamber is expanded in volume and an external face is thrust outwardly to an extended position.